1. Field of the Invention
The present invention relates to a line interpolation apparatus, for the progressive conversion, into a scanning (a progressive scanning) image signal, of an interlaced scanning image signal, obtained by decoding a signal for which image compression was performed using a vector representing the movement and the direction of movement of an image.
2. Description of the Related Art
To convert an interlaced scanning image into a progressive scanning image, conventionally, motion or lack of motion is detected based on differences in pixel values (a process hereinafter referred to as xe2x80x9cmotion detectionxe2x80x9d), and based on the result obtained, interpolation pixels are generated to produce a progressive scanning image.
In this case, when from the result obtained by motion detection it is determined that xe2x80x9can image is stationaryxe2x80x9d, adjacent pixels for field images along the time axis, e.g., upper field images and lower field images, are employed to generate an interpolation pixel that corresponds to an image position midway between the field images.
When, as the result of motion detection, it is determined that xe2x80x9can image is movingxe2x80x9d, an interpolation pixel is generated using pixels located in the same field image.
According to the conventional line interpolation method, however, since only pixel data in the vicinity of an interpolation pixel that has been generated are employed, a predetermined interpolation process is performed, even though data for the direction or the distance of the overall movement of an image can not be included. Therefore, when deterioration of image quality due to interpolation occurs, correcting the image is difficult.
To resolve this problem, it is an object of the invention to provide a line interpolation apparatus that includes additional data for the direction and distance of all motion in an image, and can therefore suppress the deterioration of image quality due to interpolation, and to provide a line interpolation method therefor.
To achieve the above object, according to a first aspect of the invention, there is provided a line interpolation apparatus, which converts an interlaced scanning image signal into a progressive scanning image signal, wherein the interlaced scanning image signal is obtained by decoding a signal, for which image compression has been performed, using a motion vector that represents the direction and distance moved in an image; and wherein, as line interpolation means, a line interpolation method is determined by using both information obtained using the motion vector and information obtained by calculating differences between a pixel to be interpolated and pixels that, in image fields aligned with the time axis of and preceding and succeeding the image field in which the pixel to be interpolated is located, spatially occupy positions corresponding to that of the pixel to be interpolated.
According to a second aspect of the invention, there is provided a line interpolation method, for converting an interlaced scanning image signal into a progressive scanning image signal, comprising the steps of: obtaining the interlaced scanning image signal by decoding a signal for which image compression has been performed by using a motion vector to represent the direction and distance moved in an image; and determining a line interpolation method, as line interpolation means, by using both information obtained from the motion vector and information obtained from differences between a pixel to be interpolated and pixels that, in image fields aligned with the time axis of and preceding and succeeding the image field in which the pixel to be interpolated is located, spatially occupy positions corresponding to that of the pixel that is to be interpolated.